Whilst do like the video I think that most of what they say is right but I think their knowledge of Self-Defence is limited to a heavy emphasis of "street fighting". I haven't watched the video in a while but is this where they mention the concept of multiple attackers too?

They dont mention multiple attackers or the non-fighting parts of self defense, wich is where it falls down. I also think that although they cover weapons (i.e. control /trap the limbs) it is hard (not impossible) to do and takes alot of time. That said, I wouldnt like to piss off a gracie :p

What Impressed me was the distrincton they made between sport and self defense, because alot of people dont, and also the triangle bit at the end. If you didnt watch it they had a pyramid and the bottom represented the thousands of sporting techniques you learn, and the top represented the small number (36) of self defense techniques. Their point was that people only learn the sport for the first few months, years, whatever, and any BJJ self defense is taught at black belt. What happens if you get attacked before black belt? Or develop bad habbits? They propose that the self defense bit is taught first, and that you only learn the sport aspect after you are 'street ready' (although I dislike that term). This basic knowledge of self defense gives you a filter, so that you can decide what is good and what is bad and stop you falling into bad habits.

If the first thing you leant was an armbar from guard you might try and pull guard in a fight and try and armbar, wich would be terible. If the first thing you leant was a takedown, sweep to rear mount and choke, that has a much higher chance og sucess

Haven't watched this video, but I'll put in some comments anyway(I have horrible down load speeds of late!). There are Gracie schools, Kron Gracie I think, that teach the 36 basic SD techniques as their white to blue program. So, those are the basics you learn first. Aside from that, positional dominance is taught first and formost before even some submissions. So, that grounding is there. The second thing to look at is the history and developement of BJJ. While there was a need for actual self-defense, a lot of the techniques grew out of challenge matches, ie. dueling. So, while there was danger of being harmed, it was almost always undrstood to be a one-on-one contest. The Gracies put a lot of time and effort into proving their system of fighting to be "the best" through these matches, and made quite a a name for themselves in the mean time. Once they had set up "style dominance" in Brazil, the challenges turned into tournaments. That is where the sport system developed and the same sort of karate vs. karate attack syndrome came about. Ever more complex techniques were needed to face someone who knew all of your basic bag of tricks. And on and on it went.

I'm always a bit confused also by their complete lack of differentiation between a "streetfight" and self-defense,

It seems that you simply can't answer questions about how a certain art is going to work without first being able to answer where exactly you want it to work - which they seem to generally refuse to do.